A slide fastener is a well-known part as an opening/closing tool for various articles. It is known that elements, which are engaging parts of the slide fastener, and stoppers can be made of metals, and particularly, those made of a copper alloy often have been used. The properties conventionally required for the fastener members made of the copper alloy are high whiteness, good smoothness, a high plating property, a high casting property and the like. As the copper alloy materials for forming the fastener, copper-nickel-zinc alloys such as nickel silver, and copper-zinc alloys such as red brass and brass are well known, and various proposals for improving these copper alloys have been made.
Japanese Patent Application Public Disclosure (KOKAI) No. H10-18046 A (Patent Document 1) discloses that to provide a method for enabling production of a slide fastener or its chains comprising copper or copper alloy elements with high glossiness and good outer surface smoothness, the elements each having composition comprising Cu: 60 to 100%, Zn: 0 to 35%, Ni: 0 to 15% and inevitable impurities are subjected to an acid treatment to smoothen the outer surfaces by immersing the elements in an acid treatment solution containing hydrogen peroxide, sulfuric acid, phosphoric acid, a surfactant and an aliphatic alcohol.
Japanese Patent Application Public Disclosure (KOKAI) No. 2003-183750 A (Patent Document 2) proposes, for the purpose of providing a copper alloy for a slide fastener having high whiteness, no nickel allergy, and good continuous casting property and casting quality, a copper alloy having composition represented by the general formula: CuaZnbMnc, where a, b, c are in mass %, a is the balance, 10≤b≤20, 8≤c≤15; and inevitable elements may be contained.
Japanese Patent Application Public Disclosure (KOKAI) No. 2003-180410 A (Patent Document 3) tries to improve surface whiteness, appearance decorativeness, and glossiness of copper alloy element member by subjecting the element to a combination of electrolytic plating and electroless plating. It discloses that the copper alloys that can be used include red brass, brass, and an alloy represented by the general formula: CuaZnbMncMdXe where M is at least one element selected from Al and Sn; X is at least one element selected from Si, Ti and Cr; a, b, c, d and e are in mass % and a is the balance; 0≤b≤22, 7≤c≤20, 0≤d≤5, 0≤e≤0.3; and inevitable elements may be contained.